US1710490A - Automatic telephone system - Google Patents

Description

April 1929- R. G. RICHARDSON ET AL 1,710,490

v AUTOMATIC TELEPHCLNE SYSTEM Original Filed Feb. 25, 1924 '7 Sheets-Shqgt l I I HY Mn g Bait-155i E.H mhar1fcm-Juhn I. Bellamy April 1929- R. G. RICHARDSON ET AL AUTOMATIC TELEPHONE SYSTEM I Original Filed Feb, 25, 1924 7 Sheets-Sheet 2 Inueumrs 3 k an Emmi-Lay .E'rfiwhard's EFL-11327.11 Ifiallamw April 23, 1929.

R. G. men/museum AL 1,710,490

AUTOMATIC TELEPHONE SYSTEII Irzuan urs Bud'nay EBmharJsun-Juhn [Bellamy April 1929- R. G. RICHARDSON ET AL 1,710,490

AUTOIIATI C TELEPHONE SYSTEM Origiflal Filed Feb. 25, -1924 '7 Sheets-Sheet 4 April 23, 1929.

R. G. RICHARDSON ET AL AUTOMATIC TELEPHONE SYSTEM Original Filed Feb. 25, 1924 7 Shets-Sheet 5 Inusn ar's BUD/Z155! EHIEhEIJJiE/H- Jul-m [Bellamyfi a A1314123, 1929- R. G. RICHARDSON ET AL AUTOMATIC TELEPHONE SYSTE" orlginal Filed Feb. 25, 1924 '7 Sheets-Sheet 6 R. G. RICHARDSON ET AL.

AUTOMATIC TELEPHONE SYSTEM Original Filed Feb. 25, 1924 April '23, 1929.

'7 Sheets-Sheet '7 W T a 7 5% W r l F mm MM 7 o v MYN Wvm 0 j n \\\.m. m rm 2 E L w .5 W Jm U H Emm EQDNEY e. RICHARDSON,

Patented Apr. 23, 1929.

warren STATES PATENT OFFICE.

or onioaeo, AnnJ'onn IQBELLAMY, or BROOKFIELD, ILLI- nors, nssrenonsrr ASSIGNMENTS, To A TOMA IC nnncrnrc: INC, on GHIGAGO, ILLINOIS, A cearona'rroiv or DELAWARE.

AUTOMATIC TELEPHONE SYSTEM.

Application filed February 25,1924, Serial No. 694,842. Renewed January 16, 1929.

The present invention relates to'automatic telephone systems in general, but is concerned more particularly with multi-oflice automatic systems of the type in which so-called directors are used to register, translate and retransmit telephone numbers; andthe obgect, broadly stated, is the production of a new and improved telephone system of the foregoing character.

A feature of the present invention is a new and improved arrangement for cutting off a director automatically at theend of the transmission of a telephone number, as to which feature the present case may beconsidered as an improvement on the eopending application of Nelson, Serial no. 578,175, iiled July 6, 1922. iln this prior case the directors are designed to receive two ofiice digits and then to receive a subscribers number consisting of a fixed number of digits, after which they are automatically cut oif. The number of digits may vary between the different oflices, but for any one office the number of digits in the subscribers number must always be the same because the cut-off in each director is controlled locallyby the advance of a sequence switch to a definite switching position. This makes it impossible to vary the number of digits in the telephone numbers except between complete of'lices, as stated, which sometimes is a serious objection. Accordingly, it is one object of the present invention to provide new and improved circuit arrangements whereby the director may be switched through automatically at a plurality of sequence switch positions, and independent of the total number of digits transmitted.

More specifically, the present invention provides circuit arrangements whereby the switching through of the director is-controlled revertively fromthe switch train employed in setting up a connection. lhe ap plicants are aware of the fact that such a revert-ive control may be accomplished in any one of a number of ways, but have chosen to illustrate the invention in connection with a system in whichthe revertive control is accomplished according to the direction of current flow in the calling loop. Two embodiments of this arrangement are shown. According to the preferred embodiment, a polarized relay in the director responds to a reversal or the trunk conductors when a connector is seized and connects up two counting relays. One of: these counting relays is operated locally when'the tens digit is transmitted to the connector and the other counting relay operates locally at the end of the units digit; When the second counting relav operates, the director is cut oif from the connection and is freed in the usual manner.

According to the desirable modification of the above mentioned scheme, thetrunk cir cuits are straight throughout the system and, when a number is called containing the maximum number of digits, the director cuts itself off automatically upon the retransmission of the last digit, due to the arrival'of the sequence switch at the switching position. In order to cut off the director at the proper time when a number is called containing a. smaller number of digits, the connector switch used for this latter number contains circuit arrangements for giving a momentary re versal of battery at the end of the units digit. This momentary reversal of battery brings about a momentary operation of the polarized relay in the director which relay now operates without the-assistance of counting relays to cut off and free the director at once.

j.Anotlier feature of the invention relates to arrangements whereby the intermediate distributing frames, which are used to facilitate changing the office codes, are greatly reduced in number. In prior systems'of this character each director had its own individual. intermediate distributing frame, but accordingto the present invention one frai'ne lS'D'lAClB to serve fora plurality of directors.

As a part of this improvement the O'illCG registers', each of which was formerly associated physically with the corresponding director, are now all mounted together side by side on shelves like ordinary Strowger switches and the banks are multipled together in the or- CllIlttl'YWZlY. This conforms more nearly to standard practice and reduces the size and complexi y of the director unit itself.

In addition to the objects pointed out hereinbefore, there are a great many improve ments mainly incidental to the carrying out of the main obj ects cited and which, together with the foregoing-will appear fully hereinafter.

Referring now to the accompanying drawings comprising Figs. 1-8, inclusive, Figs. L6, inclusive, show by means of the usual circuit diagrams a suiiicient amount of apparatus, in a telephone system embodying the common intermediate distributing frame and the preferred arrangement for revertively controlling the cut oil of the director, to enable the operation of the system to be understood; F ig. 7 is a table showing the combinations in which the relays a, .7), 0, and (Z, Fig. 5, must be operated; Fig. 8 shows a desirable modification off the scheme for revertively CODtIOllillg the cut oil of the director; and Fi 9 shows the holding circuit HO which is employed in certain trunk lines when the alternate director cut oil arrangement is used.

The line of the automatic substation A,

Fig. 1, terminates at the exchange in the line switch C. The line switch C has access to a number of trunk circuits such as TC, each of which is individual to a selector such as D. There is a secondary switch SS associated with each trunk circuit and the secondary switch SS has access to a number of directors, one of which is shown in Figs. 3-6, inclusive. A connection may be eXtende'd-under the control of the director shownfrom the line of substation A through the selector D, the selector E, the repeater F, Fig. 2, the selector G, the repeater F, the selector I, the selector J, and the connector K to the line of substation A.

The substations A and A are of the usual automatic type and each has the usual talking, signalling, and switch controlling in strumentalities.

The line switch C, Fig. 1, is mechanically of the well known rotary type in which the wipers have no normal position and move in a forward direction only. The line switch C is similar to the line switch 0. The secondary switch SS is also similar mechanically to the line switch C.

The selector D is a two motion vertical and rotary switch ofthe well known type and has its bank con tacts arranged in horizontal rows or levels. The selectors, E, G, I, and J and the connector K are of the same type of switch mechanically.

The repeater F is an automatic repeater of a well known type an d is provided to furnish talking battery to the calling subscriber from the local exchange and in order to avoid the necessity of providing three conductors in the inter-oiiice trunk line. The repeater F is assumed to be identical with the repeater F.

The complete director illustrated in F igs;

3-;6, inclusive, comprises essentially two sequence switches S and S, F1g. 3, a sender switch S F1g. 4, and four digit reglsters .DR-1-DR4, inclusive, which with the necessary relays are all assembled together or otherwise physically associated for convenience in wiring, as for example by being mounted on an individual panel or rack, and an oiiice register OR, Fig. 5, which as men cally a simple switch having the wipers 206 and 207, which are rotated in a forward direction by the stepping magnet 204 and which are restored to normal upon the energization of release magnet 205, whose circuit is controlled through the cit normal contacts 216.

The digit registers DR1DR-4;, inclusive,

Fig. 6, are similar to the sequence switch S. vThe sequence switch S is mechanically similar to the line switches C and C and to the secondary switch SS, and its wipers are moved in a forward direction only by the stepping magnet 208 and are advanced to their normal position by the operation of the same stepping magnet. sequence switch S are advanced upon the backward stroke of the stepping magnet 5208 rather than upon the forward stroke of the said stepping magnet. The sender switch S Fig. 4-, is similar to the mechanism of the sequence switch S.

The oilice register ()3. F 5, a two motion verti al and rotary switch similar to the selector D. However, the swii h OR has two rotary magnets andmay be operated in a retary movement by long steps and by short steps as will be pointed out fully hereinafter.

The intern'iediate distributin frame TDF, Fig. 5, instead of beinindividual to one director, common to a plurlity of directors, the banks of the ofi'ice regi ters oi such plurality of directors being multipled together and connected by cable to one oi the frame.

Throughout the drawings the relays which are slow acting are indicated by a shaded portion on the lower end of the core or else by a solid black portion on they upper end of the core. relay is slow to tail heel: after its circuit is opened, but that it isnot app cciably slow The wipers of the The former indicates that the to pull up owing to the fact that thejcopp er collar is placed on the heel end. of the core rather than upon the armature. end, and the arn'iature 1s accordingly attracted by means of the lines of force which lay-pass the copper collar and reach the heel piece through the air. The relays, such as line relay 6 of the line switch C, which have the black'upper portion are both slow to pull up and slow to fall back, being slow to pull up on account of the fact that the copper collar is placed on the armature end of the core between the winding and the armature itself, in which case the lines of force must first penetrate the copper collar before they can reach the armature.

The apparatus having been described more or'less in eneral thedetailed descri tion of l For the purpose of illustration it will be as sumed that the number of the subscriber at substation A, as listed 1n the directory, is

the first two digits 33 designating the desired oiiice, and the remaining four digits 123 i designating the particular substation in the desired oiiice. that ordinarily the first two digits 33 represent the first two letters of an oiiice name and are accordingly listed inthe directory as letters instead or digits. This, however, has nothing particular to do with the invention and need not be considered further herein.

Assuming now that the subscriber atsubstation A removes his receiver, line relay 6 energizes over line conductors 2 and 3 in series and places ground on private'normal conductor 4i armature 16,-thereby making the call: ing linebusy to the connector switches having access to it and closing a circuit for switching relay 5 and stepping magnet 7 in series. Line relay 6 also connects test wiper 9 to the junction of relay 5 and stepping magnet '7 at armature 17. Assuming that the trunk terminating in the bank contacts with which the wipers 8-11, inclusive, are in engagement is idle, this latter operation of line relay 6 is of no utility at this time and switching relay 5 energizes immediately in series with stepping magnet 7, seizing the trunk. In the present case, however, it will be assumed that the trunk upon which the wipers are standing isbusy, in which case test wiper 9 is in engagement with a 'grounded bank contact, and the ground potential extended to the junction of switching relay5 and stepping magnet 7 short circuits the former and operates the latter and the wipers oilthe line switch are advanced step by step in search of an idle trunk, owingto the buzzer-like action of stepping magnet 7 which interrupts its own circuit. 1

"When an idle trunk is reached, which trunk, it will be assumed, is the one comprising conductors 2142 1, inclusive, switching relay 5, being no longer short circuited, energizes in series with stepping magnet 7. Stepping magnet 7, however, does not energize at this time on account of the high resistance of switching relay 5. Upon energizing, switchrelay 5 prepares a circuit for the magnet 1301" the meter M at armature 1e; opens the test circuit and prepares the holding circuit at armature 13; and at armatures 12 and 15 disconnects line conductors 2 and 3 from the windings of line relay 6 and ground and extends them by way of wipers 8 and 11, the bank contacts. upon which they are standin conductors 21 and 2 1, the resistance 29, and

the armatures 35 and 38 to the windings of line relay 25 of the trunk circuit TC. Line re- It is understood lay 25 thereupon energizes over the calling line and closes at armature a circuit for release relay 26. The electro-polarized relay 28, however, whose right hand winding is energized from the release trunk conductor 22 through resistance 42, and whose left hand winding is energized in multiple withthe resistance 29, is not able to operate its armature at 'this time, owing to the fact that either winding alone is unable to operate the armature, and owing further to the fact that these windings are now energized in opposition to each other. Releaserelay 26 energizes responsive to the closure of its circuit at armature 31 of line relay 25 and places ground on release trunk conductor 22 atarmature 32, thereby completing a holding circuit through wiper 9 and armature 13 and its working contact for relay 5 before the slow acting line relay 6 has had time to deenergize.

- In the trunk circuit TC, release relay 26 also closes at armature 33 a circuit for switching relay 16 ofthe secondary switch SS and stepping magnet47 in series, and armature 34 connects test wiper 5-1 to the junction of the said switching relay 46 and stepping magnet 437. Accordingly, the secon'dary switch SS selects an idle trunk in the same manner as described above for the line switch 0, which trunk is assumed to be the one comprising conductors 5659, inclusive, and extending to the director shown in Figs. 3-6, inclusive. reached, switching relay a6 energizes;'opens the test circuit and places ground on test wiper 541 at armature 50, thereby grounding conductor 58; prepares the impulse circuit at armature 51; and at arinatures l8 and 19 closes a bridge across conductors 43 and 45 extending to theselector I). This bridge includes wipers 52 and 53, the bank vcontacts lVhen this idle trunk is upon which they are'standing, conductors 56 and 57, resistance 306,Fig. 4i, and armatures 029 and 331 in'multiple. Responsive to the closure oi this bridge, line relay (13 of the selector -D energizes and closes a circuit for release relay at armature 77, whereupon relay 64 energizes and prepares the switch for operation in the usual manor.

In the director, release relay 321 energizes responsive to the ground potential b ing placed upon conductor 53 by the secondary switch SS through test wiper 5 4: and pre pares the director for operation by operating its armatures 325328, inclusive.

The upper winding of the electro-pohu'ized relay 304 is now energized in multiple with relay 321 and the lower winding of the said relay is energized in multiple with resistance 306. Neither windin alone of this relay has suiiicient strength to operate the armatures. However, owing to the fact that the two windings are now energizedin the same direction, the relay operates and prepares certain circuitsto bcsubsequently closed.

at substation A, and, upon each deenergizacircuit for the slow acting relay tion, line relay 25 opens the circuit oi the slow acting release relay at armature 30, but relay 20, being slow acting, maintains its armaturcs attracted. thri'iughout the series 01 interrruations. Upon each decnergization, line relay also discoi'mects the combined switching and operating conductor from switching relay 2'? at armature 31 and con nects it to ground, thereby closing a circuit tor vertical magnet 433 oi the office register OR, Fig. 5, as follows: 'l'rom ground by way oi the resting contact and armature '31 ct line relay 25, armature 51 and its working contact, wiper 55, the bank contacts upon which it is standing, conductor 59, series relay 202, Fig. 3, wiper 207 of the sequence switch S, the first associated bank contact, conductor 221, and vertical magnet oi the oihce register "a 1 n .L 1 .1 Ohv to cattery. nesponsiv-e L-O tnc tniee unpulses of current delivered. to magnet 438 at this time, the shaft 431 ot the oitice register OR is raised three ste )s throu 'h the medium of the vertical ratchet 432, and the wipers 451-454, inclusive, are carried opposite the third level of bank contacts. The shaft is retained in its operated position by the double dog 435. Relay 202 is energized in series with vertical magnet 438 upon the first impulse of current being delivered to the latter and, being slow acting, maintains its armature 214 attracted throughout the series of impulses. Relay 202 accordingly closes a 203 which prepares at armature 215 a circuit for stepping magnet 204 of the sequence switch S.

At the end of the vertical movement of the office re; 'ster OR, slow acting relay 202 decnergizes and completes at armature 214 a circuit through armature 215 for stepy iing magnet 204, whereupon the wipers 200 and 207 of the sequence switch S are advanced into engagement with the second set oi bank contacts. A. moment later, relay 203 deenergizes, opening the circuit of stepping i'nagnct 204. When the calling subscriber manipulates his calling device in accordance with the second ottice digit 3, the three impulses of current transmitted to the director over conductor 59 and through the series relay 202 are extended by wiper 20"? of the sequence switch S by way of the second associated bank contact and conductor 222 to the long step rotary magnet 441 of the office register OR. Accordingly, the shaft 431 is'rotated three long steps through the medium of the ratchet cylinder 434. The first rotary step of the shaft 431 carries the wipers 451-454, inclusive, into engagement with the first set of bank contacts in the third level; the second step carries the wipers over the first three sets of contacts and into engagement with the fourth set of contacts; and the third step carries the wipers overthe second three sets of bank contacts in the third level and brings them into engagement with the seventh set of bank contacts in the third level, which is the first set shown as wired up on the drawings, it being understood that all the contacts in the bank may be wired up to the IDF. The slow acting series relay 202 is again energized over the operating lead, and stepping magnet 204 oi the sequence switch S is again energizerL at the end of the series of impulses,

due to the con'j it action o't relays 202 and 203, and the wipers 200 and 207 are advanced another step into engagement with the third set of bank contacts. l l iper 207 at this time extends the operating lead by way of conductor 231 to magnet 501 of the digit register Did-d, Fig. 0, and wiper 206 of the sequence switch S places ground on start conductor the said wiper 206 being grounded through armature 325 of release relay 321 and 1 through conductor 236. Responsive to the wound potential being placed upon conc tor 235, the sender is started to transmit the first code digit. However, the description of the setting of the digit registers DR-1-DR-4, inclusive, in accordance with the subscriber digits of the number will be taken up before the operation of the sender is considered.

Responsive to the manipulation of the calling device in accordance with the first subscriber digit 1, one impulse of current is transmitted to stepping magnet 501 of the digit register DR 1, Fig. 6, and wiper-505 is advanced one step into engagement with the first impulse stop conductor 491. The

sequence switch S is again advanced one step in the usual manner. Responsive to the dialling of the second subscriber digit 2, the digit register l)lt2 is set accordingly; responsive to the d lling out the third subscriber digit 3, the third digit register DB-3 is set accordingly; and responsive to the dialling of the fourth subscriber digit 4, the tourth digit register DR-4 is set accordingly,the

wipers 206 and 207 of the sequence switch :S I, being advanced one step in the herernbetore described manner at the endof each of the above mentioned digits. Accordingly, the wiper 207 is advanced into engagement with a dead contact and the wipers remain in this position until the director is freed.

- Returning now to the point at which start conductor 235 was grounded at the end of the second ofiice digit 3, the placing of the ground potential on start conductor 235 closes a circuit through the resting contact and armature 308, conductor 223, the wiper connecting relay 455, Fig. .5, conductor 224, and the short step rotary magnet 440 of the office register OR. Relay 455 accordingly now standing are connected to the intermediate distributing frame by means of the conductors 461-464, inclusive, and conductors 461 and 463 are grounded by means of the two jumpers extending therefrom to the opposite side of the frame. Accordingly, relays a and become energized and jointly place ground on the second impulse stop conductor 492 preparatory to terminating the first code digit 2.

. As a further result of the ground potential being placed upon start conductor 235, a circuit is closed through the interrupter 305 and the resting contact and armature 354 of relay 324 for sending relay 322. Upon the first closure of of the interrupter 305, relay 322 energizes and opens a point in the outgoing contrel circuit at armature 329. Armature 329, however,'is shunted at this time by armature 331 and its resting contact, and the outgoing control circuit is not opened. Relay 322 also closes at armature 330a circuit for stepping magnet 338 of the sender." Stepping magnet 338 thereupon energizes and moves itspawl into engagement with the next notch, in the associated wiper driving ratchet wheel but does not move the wipers 340 and 341.

Upon the next opening of the interrupter 305, sending relay 322 deenergizes and opens the circuit of stepping magnet 338 at armature 330, whereupon the wipers 340 and 341 are advanced into engagement with the first set of bank contacts. When this occurs, wiper 340 engages a grounded contact and pick-up relay 323 energizes; operates the two step counting relay 303 the first step in a man-' nor to be pointed out hereinafter; and at armature 331 removes the shunt from around armature 329 and its resting contact. I

Since the shunt is now removed from around armature 329 and its resting contact of sending relay 322, stepping magnet 338 is energized in the usual manner at armature 330 upon each energization of sending relay 322 subsequent to the above mentioned energization of pick-up relay 323, and, in addi tion, the outgoing control circuit is opened at armature 329, pern'iitting line relay 63 of the selector D to deenergize. Since magnet 338 is energized each time the outgoing control circuit is opened, and since the wipers 3 -0 and 341 are driven upon the back stroke ot. magnet 338, the said wipers 340 and and 341 are advanced one step immediately following each opening in the outgoing control circuit, and, upon each step of the wipers, wiper 341 engages a different one of the impulse stop conductors 491-500, inclusive. No circuit, however, is closed for'stop relay 324 when wiper 341 engages the bank contact in which stop conductor 491 termi nates, owing to the fact that stop conductor 491 is not grounded. Stop conductor 492,

however, is grounded by the conj oint'action of relays a and c as pointed out hereinbefore. Consequently, at the end of the second interruption in the outgoing control circuit at armature 329, wipers 340 and 341 advance another step and the latter engages the second impulse stop conductor 492, closing the following circuit for stop relay 324: from;

ground by way of the right hand armature and working contactot relay a, Flg. 5, mid- "dle armature and resting contact of relay 6,

middle armature and working contact of relay c, the second impulse stop conductor 492, the third contact in the bank of wiper 341, wiper 341, and stop relay 324 to battery. Stop relay 324 thereupon energizes; causes the complete energization of counting relay 303, in a mannerto be hereinafter described, by openin g its initial circuit at armature 336; and. at

armature 334 disconnects sending relay 322 from the. interrupter 305 while the said relay is still in a 'deenergized condition, thereby terminating the first code digit 2. Stop relay 324 also closes a locking circuit for itself at armature 336 through the working contact and armature 332 of pick-up relay 323,- and at armature 335 closes a restoring circuit for stepping magnet 338 through interrupter contacts 339. Accordingly, the wipers 340 and 341 are rapidly spun around until wiper 340 passes oil the last grounded bank contact, opening the restoring circuit of magnet Viper 340 also opens the circuit of pick-up relay 323. This relay, howcver,'is slow acting and maintains its armature attracted for an interval after its circuit is opened.

' In the selector D, Fig. 1, line relay 03 is deenergized twice, momentarily, responsive to the two interruptions produced in the outgoing control circuit of the director as above described, and closes a circuit upon each deenergization for vertical magnet 71 as tollows: from ground by way of armature 85 and its resting contact, armature 77 and its resting contact, armature 7 9 and its working contact, slow acting series relay 65,-arinatui.'e 36 and its resting contact, and vertical magnet 71 to battery. By the operation of vertical magnet 71, the wipers of the switch D are raised step by step until they stand opposite the second level of bank contacts. Ralay is energized in series with vertical magnet 71 and, being slow acting, it maintains its armature attracted throughout the vertical movement. 7

By the conjoint action of series relay 65 and off normal contacts 76', which close upon the first vertical step of the switch, a circuit isclo'sed for stepping relay 66. Relay 66 thereupon energizes and closes a locking circuit for itself at armature 81. This locking circuit includes the interrupter contacts V and armature and its resting contact in addition to off normal contacts 76. Relay 66 also prepares a circuit for rotary magnet 72 at armature 82.

At the end of the series of impulses de- .livered to vertical magnet 71, slow acting series-relay deenergizes and completes the circuit of rotary magnet 72 at the normally closed contacts controlled by armature 80, whereupon rotary magnet 7 2 energizes and advances the wipers 68-70, inclusive, into engagement with the first set ofbank contacts in the selected level, the second, and, near the end of its stroke, opens the circuit oi stepping relay 66 at itsintorruptcr contacts 72. Responsive to this, stepping relay 66 deenergizes and opens the circuit ofrotary magnet 72 at armature 82, whereupon rotary magnet 72 decnergizcs also and again closes its interrupter contacts 75.

In case the trunlr terminating in the first set of bank cont-acts is idle, switching relay 67- energizes immediately upon the above closure of the interrupter contacts and seizes the trunk. In this case, however, it will he assumed that the trunk terminating in the first set Oil' bank contacts is busy, in which case test wiper (39- engages a grounded test contact and switching relay 67- is short circuit-ed. Also stepping relay 66 energizes through test wiper 69 and again closes a circuit for rotary magnet 72at armature 82, whcreuponrotary magnet 72 energizes again and advances the wipers GS TO, inclusive, into engagement w-itliithe next set of bank contacts.

This alternate operation of stepping relay 66 and rotary magnet 72 continues until an idle trunk is reached, which trunk, itwill be assumed, is the one comprising conductors 87-89, inclusive, and extending to the selector E, whereupon switching relay 67,. being no longer short circuited, energizes in series with stepping relay 66, stepping: relay 66 not encrgizing on account of the high resistance of switching relay 67. Upon. energizing, switching relay 07 disconnects ground 'f'lfill'l armature 77 of line relay 63 at armature 85, there-- by opening the circuit of the slow acting release relay 643; shifts test wiper 69 from the test circuit to the holding circuit at armature 84a; and at arinatures 83 and 86 disconnects trunlr conductors 4-3 and ll) from the windings of line relay 63, and extends them by way oil wipers 68 and 70, the bank contacts with which they are in engagement, and conductors 89 and 87 to the windings ot' the line relay of the selector l he line and release relays (not shown) of the selector E now on ergize in the usual manner and the latter prepares the switch for operation in the usual manner.

In the director, the clcctro-pol'arized relay 304 now retract-s its armatures 316 and 317, owing to the fact that the current flow in its lower winding new opposes the current flow in its: upper Winding on account of the reversal made in conductors 87 and89 leading from the banks of the selector D to the selector E, Fig. 1. Upon the retraction of armature 316 of relay 304, the two step counting relay 803, whose locking circuit iscontrollcd by armature 316, de -energizes.-

After the interval for which it is adjusted, slow acting pick-up relay 0t thescnder deenergizes and opens the locking circuit of stop relay 824 at armature 332. Stop relay 824 however, is slow acting also and does not cleener-gize'immediately. Pick-up relay 323 also closes at armature acircuit for the short step rotary magnet 440 of the ofiicc ister OR, Fig. 5, as follows: from ground by way of armature 3100f relay 301-, Fig. 4, and its resting contact, working contact and armature 337, armature 3,33 and its resting contact, conductor 2%, and magne 459:0 to battery. Responsive to the closure of this circuit, magnet 4A0 energizes and operates the rat'chct wheel 433 through the medium of the member sec, advancing the wipers 451-41541, inclusive, one shortstop. lhe closure of the above circuit results in the wiper connecting relay L55 being short circuit'ed. -When this occurs, relay 4-55 deenergizcs and disconnects the wipers of the. ofiice register QR. This is done soas to permit the relays (Zr-(ls inclusive, to energize anew after each digit; Otherwise, one of these relays which is called upon to energize completely during one digit and to energize part ay during the succeeding digit might remain operated completely from the half voltage battery which ordinarily oper-' ates it only halfway.

In the sender, Fig. 4:, the slow acting stop relay 324: deenergizes after an interval; opens the circuit of magnet 4 1001? the office register OR at armature 337;, and at armature again connects up the sending relay 322, whereupon the said sending relay starts to vibrate again under the control of the interrupter 305 to send out the second code digit l.

Responsive to the dcenergization of the short stop rotary magnet &0 oil: theollice register {ll the circuit of the win r connecting v relay is again closed at the interrupter contacts 439, whereupon the wipers are again connected up and relay (4 becomes energized over conductor Ml and through the associatcdIDl juniper. This relay appli s ground to the fourth impulse stop CUllClllCLOl sill.

it may be pointed out conveniently at this time that the interval required for the slow acting relays and 32st to all baclr one after the other as above described is utilized to give time for the change-over and trunlz hunt 1g operations to taue place in the automatic switches, for example, the change-over and trunlchunting operations of the selector D,

1, above described.

As above pointed out, the sender is again started and is. new transmitting the second code digit4 in the desired number, and, at the cuit forstop relay 324 as follows: from' ground by way of the right hand armature and working contact ofrelay a, Fig. 5, middle armature and restin contact of relay Z), middle'armature and resting contact of relay 0, second armature and resting contact (counting from the left) of relay d,the fourth impulse stop conductor 494, the corresponding contact in the sender bank, wiper 341, and stop relay 324 to battery. Responsive to the energization of stop relay 324, the second code digit is terminated in the usual manner.

Responsive to the transmission of the second code'digit 4, the selector E, Fig. 1, raises its wipers opposite the fourth level and ro tates them into engagement with an idle trunk, which trunk, it will be assumed, is the one comprising conductors 9092, inclusive, and extending to the repeater F. Responsive tov the seizure of the repeater F, line relay 102 energizes over conductors 90 and 92 and closes a bridge across the associated outgoing trunk conductors extending to the dlstant selector G at armature 107. This br1dge 1neludes the right hand repeating coil windings and the upper Winding of the electro-polarized relay 101. Relay 101, however, does not operate at this time on account of the fact that the current flow in its upper winding is insufficient to operatively energize the relay. Responsive to the closure of the bridge across the outgoing trunk conductors at armature 107, the line and release relays (the latter not shown) of the distant selector G energize and prepare the switch for operation. As a further result of the energization of line relay 102 of the repeater F, it closes at armature 106 a circuit for release relay 103, whereupon re lease relay 103 energizes an d places ground on release trunk conductor 91 at armature'108, and at armature 109 closes a circuit for the lower winding of the electro-polarized relay 101. Relay 101 now energizes and reverses the trunk coniiluctors 90 and 92. Relay 101 energizes at this time on account of the fact that the current flow in the upper winding assists the current flow in the lower winding of the relay, due to the reversal in the leads connecting theline relay of the distant selector G with the associated trunk conductors.

In the director, the electro-polarized relay 304 again energizes responsiveto the above reversal of the trunk conductors at the repeater F. Upon energizing, relay 304 prepares a locking circuit for the relays 302 and 303 at armature 316, and at armature 317 We pares an energizing circuit for the lower winding of relay 303.

After the usual interval, the slow acting pick-iup relay 323 again falls back, responsive to its circuit being opened by the return to normal of the wiper 340, and closes at armature 333 previously traced circuit for the short step rotary magnet 440 of the office register OR, whereupon the wipers 451-454,

inclusive, are advanced into engagement with v the third and last set of bank contacts associated with the called office, and, as soon as relay 455 energizes again upon the subse-' quent deenergization of rotary magnet 440, the wipers are again connected up and relays aand (Z energize over conductors 481 and 484, respectively, and the associated IDF jumpers. 7 Relay 0 is energized also at this time over conductor 483 and through the associated IDF jumper. The relay 0, however, gets only half as much current at this time as is required to operate it fully, owing to the fact that the jumper associated with conductor 483 extends to a half voltage battery busbar instead of to ground, and the drop across relay 0 is equal to the difference between the potential of the regular exchange battery and the potential of the half voltage bus-bar. The battery associated with the half voltage bus-bar may be a separate battery of the same polarity as the regular exchange battery which is used to operate the relays a(Z, inclusive, or it may be the grounded half of the regular exchange battery itself, depending upon which is found to be the most desirable in any particular case. At any rate, the current flow through the relay 0 at this timeis only half as great as it is when the free terminal of relay 0 is grounded. Accordingly, the relay 0 is operated only to the extent of the first step. Accordingly, its contacts marked 1 close while the remaining contacts marked 2 remain unoperated. As a result, the conductors 226 and 230 are joined together at the left hand armature of the relay 0 in order to operate the transfer relay 301, as will be described hereinafter.

The sender is again started in the usual. manner to transmit the third code digit 3, and, due to the fact that the eleetro-polarized relay 304 is now energized as above pointed out, theenergization ofpicleup relay 323 results in'the two step relay 302 being operated through its first step in a manner to be explained hereinafter.

At the end of the third interrlmtion in the outgoing control circuit, wiper 341 is advanced into engagement with the contactin which the third impulse stop conductor 493 is terminated, thereby closing a circuit for step relay 324 as follows: from ground by way of the right hand armature and work-' third impulse stop conductor 493, the assoand the closure oi? the above circuit, stop relay 324i energizes and terminates the digit beoutact in the sender bank, wiper 341, stop relay 324i to battery. Responsive to bag transmitte' "1n the hereinbeiore described manner, causing the wipers 340 and 341 to be returned to their normal posit-ions. Also the initial circuit of .the lower winding of relay 303 is opened at .ar-n'iature 336, resulting in the complete energization of relay 303 in a manner to be pointed out hereinafter. As a further rest it of the energization of stop relay 324, a circuit is closed at armature 337 for the transfer relay 301, owing to the fact that relay 0 is now energized through its first step only, as above pointed out. The circuit of transfer relay 301 is as follows: from ground by way 01 armature 810 and its resting contact, working contact and armature 337, armature 3 33 and its working contact, conductor 226,, normally closed contacts con.- trolled by the leitthand armature of relay 0, working contact and left hand aiiniature of relay 0,, the associated 'stance, conductor 23.0, and marginally adjusted relay 361, and

the lower winding of relay 301 to battery. Relay 001 energizes over this circuit, but relay 8 51, being marginally adjusted, does not energize due to the high resistance associated with the left hand armature of relay 0. Relay 301, upon energizing, closes a locking circuit for its upper winding at armature 309:; disconnects ground from the working contact of armature '38? of the stop relay at armature 310 and grounds the subscriber-digit stopconduetor control wiper 211 of the sequence SWltCll it through conductor 229; opens the circuit of the oilice register wiper connecting relay e55, Fig. 4:, at armature 308 and prepares a stepping circuit for the magnet 208 i ch S at armature 307.

lhe circuits transn'iission ot' the first subscriber dig-it in accordance with the setting or". the first digit register Dll1 as soon as the slow acting stop relay 32d of the sender has fallen back.

lesponsive to the transmission of the third code digit 8, line relay 102 of the repeater F, Fig. 2, is deenergized once responsive to each of the three interruptions produced in its circuit by the sender, and, upon each deenergization, opens the circuit of the line relay oi the selector G. Accordingly, the selector G raises its wipers opposite the third lore]. and selects an idle trunk, the trunl; extending to the outgoing repeater F, tor example. Accordingly, the relays oi the repeater l operate in the same manner as described for the relays of the repeater F and the distant thousands selector 1 in the called otlice is prepared for operation in the usual manner. However, owing to the fact that there is no reversal in the trunk leading from the repeater F to the selector 1, the relay in the repeater F which corresponds to the elcctropolarized relay 101 oi the repeater F does not energize and accordingly there new no. reversal in the trunk conductors eX- tending ahead from the repeater i the reversed line relay of the selector (i having been cut oil, and the electro-polarized relay 101 of the repeater F deenergizes and strengthens out the trunk conductors and 92,1due to the tact that the current How in its upper winding now opposes the current flow in its lower winding. I

In the d-irector,the electro-polarized relay 80 i now deenergizes responsive to the re versal ot the current flow back to normal by the electro-polarized relay .ot the. repeater F and opens the locking circuit of the two step relay 303 at arn; u-re 216;, whereupon relay 303 deene-rgizes also.

After the usual interval, the sender is started upon the deenergization oi the slow acting stop relay 324:. At this tune,

gizes and moves the associated pawl into onenent with the next notch in the wiper driving ratchet wheel but does not move the wipers 210 and 21 1. V

the end -;t the single impulse representing the first subscriber digit- 1, wiper 341 of the sender is advanced into engagement with the bank contact in which the first iniipulse stopconductor 4:91 is terminated, Whereupon stop relay 32d is energized over the following circuit: ii on ground by way of armature 310 and its working contact of transfer relay 301, stop conductor control wiper 211, the first subscriber digit stop conductor 24.1, wiper 505 of the digit register DR-1, the second associated bank contact, the first impulse stop conductor 4:91, the corresponding contact in the sender bank, wiper 34:1, and stop relay 324- to battery, Upon energizing, stop relay 324i disconnects the sending relay and closes the usual restoring circuittor stepping magnet 338 at armatures 38d and 3235, respectively, and, in addition, opens the circuit of steppingmagnet 208 of the sequence switch S and closes its local self-locking circuit at armature 336. itesponsive to the opening of the circuit of stepping magnet 208, the wipers 210 and 211 l? the sequence switch S are advanced one step and the stop conductorcontrol wiper 211 removes ground from the first subscriber d, "it stop conductor 241 and places ground instead on the second. subscriber digit stop conductor -.2- l2.. v

end of the second interruption in the outgoing control circuit responsiveto the energization of stop relay 324. over the following circuit: from ground by way of armature 310 of the transferrelay 301 and its working contact, stop conductor control. wiper 211 the sequence switch S,'conductor 242,.wiper 506 of the seconddigit register DR2,the third associated bank contact, the SGCOIlClllD- pulse stopconductor 492, the corresponding contact in the sender bank, wiper-341, and stop relay 324 to battery. The wipers of the sequence switch S are advanced one step responsive to the opening of the circuit stepping magnet 208 at armature 336 of stop relay 324. V H p v i Responsive to the transmission of the second subscriber digit 2, thehundreds selector J, Fig. 2, raises its wipers opposite the. second level and selects an idle trunkin the usual manner, which trunln it will bees sinned, is the one comprising conductors 121123, inclusive, and extending tothe connector K. Accordingly, line relay 125 becomes energized and closes at'ar nature 134 p a circuit for release relay 126. Upon energizing, release relay 126 prepares the switch for operation by attracting arinatures- 135F137, inclusive. 7 7

Since conductors 121 and 123 are reversed between the connector K and the banks-of the selector J, the electro-polarized relay (not shown) in the repeater F whichjrelay 001* responds tothe clectro-polarized relay 101 oi the selector F, energizesand reverses the incoming trunk conductors, whcreuponthc direction of current flow in the upper winding of the clectro-polarizcd relay 101- of the repeater-.1 is reversed and the said relay 101 operates, reversing trunk co-nductors 90 and 92. Responsiveto the reversal of thefltrunk conductors 90 and 92, the electro-polarized relay 304, Fig. 4, responds, operatingarmaiurcs 316 and 317. r

The sender is again started in the'usual manner to send out the third su scriber digit 3 in the desired number and pick-up relay323 energizes as usual. At this tin1e,'since relay 304 is operated, acircuit isclosed through the working contact and arinature317 and arma-i ture 315 and its resting contact "for the lower winding of the two step relay 303 in multiple with magnet 208 of the sequenceswitch "S.

ikccordinb'ly, relay 303' energizes way.

roiay 303,

and operates its lightly adjusted first step armature 314, the stifliy adjusted second step armature 315 not-operating at this time on "the grounded release trunk conductor 58.

This locking circuit does not become effective at; thistiine, however, owing to the fact that theinitial circuit of the relay is still established, short circuiting the upper W nding of the relay. i

At the end of the thirdinterruption pro duced in the outgoing control circuit by the sending relay 322, the wipers 340and 341 of the sender are advanced into engagement with the fourth set of associated bank con tacts, whereuponstop relay 324 energizes over the following circuit: from ground by way of the stop conductor control wiper 211 ofthe sequence switch S, thethirdsubscriber digit stop conductor 243, wiper 507 of the digit register DR3, the fourth associated bank contact,,the third impulse stop conductor 493, thecorresponding contact in the sender bank, wiper 341, and stop relay 324 to battery. Stop relay 324, upon energizing, terminatesthe third subscriber digit in the usual manner; and, in addition, opens the circuit of stepping magnot 208of the sequenceswitchS' and of the lower winding of the .two step relay 203 and closes its usual locking clrcuit at armature 336. V] hen the initial circuit of relay 303 is opened, its 10- cal locking circuit, including its two wind- .ingsin series, becomes effective, whereupon the inagneticpull of the core is increased .to

such an extent that the second step armature 315 is operated, disconnectingthe initialenergiaing conductor from the unction of its gown winding and extends it through the resting contact and armature 315 to thejuuction of the windings of the two step counting relay 302.

In, the connectorK, lino-relay 125 is deen- ,ergized three times responsive to thetrans- 11121881011131 the third subscriber digit 3 and,

upon each deenergization, closes a; circuit for vert cal magnet 158, the circult at the time of ts first closure being as follows from ground by way of armature 134 and its resting contact, armature 1.37. andits workingcontact, contact of normal. sprlng 157 and said spr1ng,slow acting series'relay 127, and verticalinagnet 158 tobattery. By the operation of vertical magnet 158, the wipers l52 15 4,,inclusive, are raised opposite the third level of bank contacts, which is'the level. in which the line of substationA terminates, Relay 127 is energized in series .with velticlllgmagnet and, being slo'W acti i'iaintains its armature 138 attracted 'cal step. ment, slow, acting series relay 12'! deenerthroughout the vertical movement, and maintains its own circuit and that of vertical magnet 1T8 intact after the off normal springs have shifted, as they do upon the first verti- At the end of the vertical movegizes and transfers the operating circuit from vertical magnet 158 to rotary magnet 159.

In the director, the sender is again started to transmit the fourth and last subscriber digit 4;, and, upon the energization of pick-up relay 323, the usual circuit for stepping maging the usual locking circuit including both windings in series.

At the end of the fourth interruption produced in the outgoing control circuit by sending relay 322, stoprclay 32 1 is energized over the following circuit: from ground by way of wiper 211 of the sequence switch S, the fourth subscriber digit stop conductor 24%, wiper 508 of the fourth digit register DR4L, the fifth associated bank contact, the fourthimpulse stop conductor 194, the corresponing contact in the sender bank, wiper 34:1, and stop relay to battery. Responsive to the energization of relay 324, the digit being transmitted is'terminated in the usual manner and the circuit of magnet 208 of the sequence switch S, as well as the circuit of the lower winding of the two step counting relay 302 is opened at armature 336 Incidentally, the wipers of the sequence switch S are advanced responsive to the deenergization of the magnet 208, and, responsive to the'opening of the initial circuit of relay 302, the locking circuitincluding both windings of the said relay and armature 311 and its working contact becomes effective, whereupon the, re lay operates the remaining distance; opens a further point in its initial circuit at armature 313; and at armature 312 places ground on the combined operating and switching conductor 59, closing a circuit over the said conductor. 59, the corresponding contact in the bank of wiper of the secondary switch SS, Fig. 1, wiper 55, working contact and armature 51, armature 31 and its working contact,

and switching relay 27 to battery. Relay 27 thereupon energizes and closes a locking circuit for itself at armature 37; separates series rclay of the selector D from vertical magnet 71 at armature 86 for a purpose to be,

pointed out hereinafterdisconnects con- 7 "ductors 21 and 24: from the windin s of line z: I

relay 25 at armatures 35 and 38, at the same time joining these conductors with the conductors 43 and 15 of the selector D and disconnecting the latter from the control bridge including the contacts of the sending relay 322 ofthe sender. Thee-witches involved in the connection are now held up from the called line rather than from the above mentioned control bridge.

.Responsive to line relay 25 of the'trunk circuit TC being disconnected by switching relay 27 as above polnted out, the said relay deenergizes and opens'the circuit of release relay 26 at armature 30. After the interval for which it is adjusted, releaserelay 26 deenergizes and removes ground from release trunk conductor 22 at armature 32, leaving the said conductor grounded throughthe re lease trunk conductor connection extending to the repeater F. IR-elease relay 26 also opens a further point in the test circuit of the secondary switch SSat armature 31,-and

at armature 33 opens'the circuit of switching relay 46, whereupon relay t6 deenergizes, freeing the director. y

In the director, relays 301301-, inclusive, and relay 321 deenergize responsive to the removal of the ground potential from the release trunk conductor 58 when the director is freed by the secondary switch SS, and relay 321 closes at armature 325 a restoring circuit for the sequence switch S which includes conductor 237, the contacts in the bank of wiper 210, wiper 210, interrupter contacts 209, and stepping magnet 208. Stepping magnet208 accordingly interrupts its own circuit and advances the wipers 210 and 211 step by stop until the former passes oil the last grounded bank contact. 321 also closes the normal restoring circuit of the sender at armature 326, which is effec- Release relay tive in restoring the wipers 340 and 341 to normal in casethe director is'freed while a digit 1s being transnntted, 1n which case the restoring circuit at armature 335 of stop re lay 324: is not available. As a further result of the deenergizatlon of release relay 321, ground s placed on the release conductor 225 at armature 3-27, closing-a circuit through off normal contacts 216- tor releaseniagnet .205

I izlagnet' 205 therei of the sequence switch S. upon energizes and restores the wipers 206 and 207 to normal, whereupon its circiutis opened at off normal contacts 216. Asafurther result of the ground potential being placed on release conductor 225, circuits are closed through ofi normal contacts 513-516,

inclusive, for the release magnets 509512, in-

elusive, of the digitregisters DR1DR--,

inclusive, respectively, whereupon the wipers 505508, inclusive, are restored to their respective normal posit ons and the saidbif normal contacts 51351 6, inclusive, open the circuits of the, respective associated release. magnets. V Asa still further resultofthe;ap-

plication of the ground potential to release conductor 225, a circuit'is closed through release Ina-net 44-2 01" the office re istor OR and switches of the same "eneral t 1 3e. The di-' 22 rector is now completely restored to normal position and is ready to be used in handling another call.- 1 I v 1nthe connector K, Fig. 2, line'relay 125 'deenergizcd four times responsive to the transmission of the last digit 4; in the number and, upon each'deencrgization, transmits an impulse of current to rotaryn agnet 159 over the following circuit: from ground by way of armature and its resting contact, arm ature 187 and itsworking' contact, normally open contacts controlled by off normal spring 152 armature 138 and its resting contact, resting contact and armature 14-3, armature 150 and its restin contact, and rotary magnet 159 to battery. 13y the opeiat'ionoi rotary magnet159, the wipers 152451, inclusive, er the connector K are rotated step by they come into engagement with the fourth set of bank contacts in the third level, which is the set in which the line o1" substation A terminates. Relay 130 is energized in multiple with rotary magnet 159 and, being slow acting, maintains its armature attracted throughout the rotary movement. Upon energizing, relay 130' disconnects t iiper 153 from the upper winding of switching relay 131 and connects it to busy relay 129 1nstead, and at armature 146 placesa shunt around armature 1 13 and its resting contact so as to guard the circuit of rotary magnet 159 against'the possibi'lty of being opened in case busy relay 129 energizes due to test wiper From this-point the opcrationof the con nector K depends upon whether the called I noimally closed contacts controlled by arma ture 11th for busy relay 29 as 'i ollowszfrom Q'rorunfl by 'way of the working-contact and armature 136, armature 14:2 and its working); contact, normally closed contacts controlled by armaturel l, and busy relay 129 'to battery. Busy relay 129 maintains open,

the circuitoll relay 130 and rotary magnet 159 at armature 1 13 so as to prevent'any -further operation of the rotary magnet iii-case thecalling subscriber again manipulates his call 'ing device. fiusy relay 129 also connects the busy lead 161 at armature l'l l to the low r step until.

passing over the grounded bank} contacts associated with busy lines.

heavy talkingconductor, thereby transmitting an audible busy signal back to the calling subscriber to inform him that hc cannot obtain the desired connection for the time being. -Upon hearing this busy signal, the ailing subscriber is expected to replace his receiver, whereupon the connection relezscd'in a'manncr to lee-described hereinafter,

ASSLHHlIIQ'DOW that the called line isidle, busy relay 129 is not energized when the called line is reached, and, upon the deenerg'ization o1 v slowacting relay 130, a circuit closed tor the upper winding oit switching relay 181 as follows: from ground by wayotthe working contact andar nature 13o, armature 142 of busyrelay 129 and its rest ing contact, upper winding ofswitching relay 131, resting'contact and armature 1 1-5,

test wiper 153, the bank contact with'which it is in engagement, switching relay 171 of line switch (1, and the associated St-BPPIDQ magnet to battery. Relays 131 and171 enerin seriesoverthis circuit and relay 171 disconnec's the normal ground and battery connections from the called-line, but, due to a mechani al inter-locking device (not shown) between the armature oat relay 171 and the armature of relay 172, relay '171 is operated only about half way and the line" switch wipers are not conne .ed up.

In the connector K, relay 131, upon ener- *gjizing, closes a locking circuit for its lower finding at armature 149; places direct ground on test Wiper 153 at armature 148 die connects relay 130 and magnet 159 at armature 150; and at arn'iatures 14:7 and 151 connects up the line wipers, whereupon ringing current from the grounded generator lead 1601s projected'out over line wiper 154: and

returns by way (it line wiper 152, and the up per winding; of ring-outed relay 238; Re-

lay 288 is not operated at this time, however, due to its special slow acting; construction and due to the tact that no direct current flows in this circuit owing to. the condenser which is inseries with the bridgcd bcll at the called sultill/1011 A. The small condenser 181 permits enough of the return ring-- ingcurrent to lealr back to the tall'iing' circuit to give the callingsubscriber an audible in dication thatthe called subscribcfs bell is being rung. y

Considering now the electro-polarized re lay 28, associated with the trunk circuit TC, thisrelay is not operated after the'connectio' isswitched through by switching relay 27. Urdin arily, it would be expected that thisrcl say would operate due to the fact that conductors 87 and 89 leading to the selector. E are reversed. This reversal, however, is coi hen sated for by the reversal at the electro polarized relay 101 o1 tile 1 6136111361 F, Which relay is operatedv due to the reversal above inen- 1101166. n: the repeater F, which reversal in ings of the line relay 125.

turn is brought about by the reversal in the trunk conductors 121 and 128 leading from the banlrs'of the selector J to the connector K.

l hcn the called subscriber responds to the ringing of his hell by removing his receiver, a direct current bridge is closed across the conductors of his line through the transmitter and receiver, whereupon the rin -cut-otl relay 238 energizes over the called line and through the grounded generator lead 160 and closes a locking circuit for its lower winding at armature 140, and at arn'iatures 139 and 141 disconnects the wipers 152 and 154 from its own Jwinding and the lead 160 andconnectsthem instead. to the wind ingso'f the back bridge relay 124. When this occurs, relay 124 ener- L conductors 121 and 123 as regards their connection with the Windi Vhen this occurs, the current flows through the conductors 121 and 128 in the normal direction and the electlfO-POltti'lZQCl relay (not shown) of the repeater ll" retracts its armatures, reversing the associated, trunk conductors back to normal. Responsive to this, the electro-polarized relay 101 of the repeater F retracts its armatures, reversing the current flow in the conductors 90 and 92 back to normal. Responsive to this latter operation, the electro-polarized relay i8 attracts it armatures due to the reversal in conductors 87 and 89 of the selector 12;. short circuits the resistance 42 at armature 41 so as to enable the right hand winding of the relay to maintain the relay operated independent of the left hand winding; places a shunt aroundits left hand winding and the resistance 27 at armature 40; and at armature 39 closes a circuit for the magnet 18 otthe meter M over conductor 23, the corresponding contact in the bank of wiper 10, wiper 10, and. the working contact and armature 14. The u'iagnet of the meter M now operates to register the completed connection. The call ing and called. subscriber may now converse with each other as desired.

When the conversation is completed, the two subscribers hang up their receivers and, when the receiver is replaced at the called substation 11, back bri l go relay 124 dcenergizes and reverses the trunk conductors 121 and 123 back to their original standing, whereupon tl 1c electro-polarized relay (not shown) of the repeater l1" again operates and reverses the conductors extending bac tothe repeater F, whereupon the electro-polarized rel 101 opcrates and reverses the conductors 91 and 92.

his, however, does not have any effect upon the electro-pola-rizedrelay 28 associated With the trunl: circuit TC, owing to theil act that the left hand winding of the said relay 28 is nowshort circuited.

When the receiver is replaced at substation lino relay 102 of the repeater F deenerarmature to normal position in the usual manner.

circuit of the line relay (not shown)'ofthe mature 108 removes ground from release trunk conductor 91, whereupon switching'relay 67 or the selector D, switching relay 27,

the electro-polarized relay 28 of the trunk circuit TC, and switching relay 5 of the line switch C deenerglze. Responsive to the deenergization of swi'tcl'iing relay 67 of the se lectoi' D, release magnet 73 energizes through armature and its resting contact, armature 7 T7 and its resting contact, armature79 and its resting contact, and oil normal contacts 74. i.

ne wipers oi the selector D are restored to normal in the usual manner responslve to the operation of release magnet 73, whose circuit is again opened atoll normal contacts 7 4 when the wipers of the switch reach their nor mal position.

Responsive to the deenergiza-tion of the electro-polarizcd relay 28, and to the deenerglzation of switchlng relay 501 the 11116 switch G, the circuit of the magnet 18 of: the meter M is opened at arn1atures39 and 14; 7

After the interval for whichit is adjusted, the release relay (not shown) of the repeater 1 Fig. 2, deencrgizes and permits the sclector G to be restored to normal position in the usual manner.

A-fter the interval for which a is adjusted,

release relay 120 of theconnector K deenerguess and removes ground from releasetrunk conductor 122 at armature 135,permitting the selectors I andJ to be restored to normal position in the usual manner. As a further result of the ground potential being removed from release trunlrconductor 122, relays 128 and 131 deenergize and the latter disconnects the switch wipers, the removal of the ground from wiper 153 permitting relay 171 of the Release relay line switch C to deenergize;

126 also completes at armature 187 a circuit includingarmamure 134 and off normal contacts 156 for release magnet 155, whereupon the wipers of the connector K are restored The entire connection is now released andthe apparatus used therein is ready to be used in another call; V j

In order to enable certain desirable features ofthe present invention to be understood best, it will be assumed that a subscriber, the subscriber at substation A, starts;

to make a call, but, after removing his reaiao , are now iii-readiness for the first digit in the desired, number to be transmitted, but, as as sinned above, the subscriber does not manipulate his calling device, and, unless special arrangeinents were made to prevent this, the director. would remain tied up indefinitely. l iccordingl y, the two step relay 201 and the associated circuit arrangements have been,

provided to cut oil the director and extend the calling line to the first selector 1) alter a reasonablc amount of time has been given for the calling subscriber to dial the first digit. The

detailed description o'l theoperation will now be given. 7 I. v 1

When therelease relay 321 of the director,

2351 is connected to conductor-228 at armature 828, and, as soon atterthis occurs as the pro ing contact for the lower winding of the two step relay 201. Relay 201 is similar to the relays 302 and 303 and accordingly operates through the step only and prepares the usual locking circuit foritsell at armature 212; Shortly after this occurs, the projection on the periphery of the cam 352 passes from under the associated contact spr1ng, pening theinitial circuit of relay 201. Responsive to this, relay 201 pulls up completely, its two windings being energized in series over the following circu t from ground by way of armature 325 ol relay 321 and its working qcontact, conductor 236, wiper 206 of the sequence switch d,armature 212 and its work 'ing contact, and relay201 to battery. Relay 201, upon, operating completely, opens a further point in its, initial circuit and connects conductor 228with the combined switching and. operating conductor 59. The circuitsare now in readiness for switching relay 27 of the trunk circuit TO to operate to switch the connection through to the selector D and cut oil the director in case the firstdigit is not dialled before the common conductor 851, Fig. 4;, is agai rounded.

Pia

ln casethe first digit is dialled prior to this j time, tli wipers 206 and 207 arev advanced at the end ot this digit in the hereinbefore de Fig.4, energizes responsive to the release trunk conductor 58 becoming grounded when S the director is seized, the common conductor scribed manner, and the locking circuit of oil the first grounded bank contact, whereupon relay 201 deenergizes. VVithits locking circuit opened and its upper winding discon-' nected, relay 201 cannot be operated through oil in the hereinbetore described manner when a complete number is called. Assumi ng, however, that the first digit is not dialled betore conductor 351 is again grounded, the ground potential is extended through the working contact and armature 328, conductor 22S, and armature 213 and its working contact to the combined switching and operating conductor 59. Responsive to this conductor being'grounded, switching relay 27 of the trunk circuit TC isoperated and the director is freed in the hereinbefore described manner.

As pointed out. hereinbetore, series relay relay 201 is opened when wiper 206 passes I its second step again and the director is cut 7 is disconnected from vertical magnet 71 at armature-86 of switching relay 27. Accordingly, the calling subscriber is prevented from operating'the selector D directly and the connection cannot be extended any further, and

the fact that a permanent. exists vonsthe electorD may be detected by the exchange attendant in any well known or desired'manner.

It may well be pointed out at this time just why the two reversals in the trunk conductors employed when a connection is set up between the subscriber at substation A and the sub scriber atjsubstation A are made and why they are made where they are. Starting first with the reversal in the trunk conductors 121 and 123 extending between the bank of the selector J, Fig. 2, and the connector K, this reversal, as is apparent from the foregoing, is made in order to operate the electro-polarized relay SOstof the director, Fig. 4, so as to connect up. the counting relays 302 and 303 to enablethem to cut oil the director at the endot the second digit dialled atter such reversal is encountered. This permits of a variable number of selectors being used before the connector is encountered. For example, a telephone number may be called which containstwo oiiice digits and only two or three subscriber digits, depending upon the size of the called oliice. In either case, however, thetrunk conductors leading to the connector when such oflice is called are reversed and the director is automaticallycut oil in the hereinbefore described manner.

The-second. reversal, that is, the one between the bank of selector D and, selector E, is necessary in ord r to con'ipensate for the first reversal after the director is cut oil and before the called man answers so that the calling subscribers meter. will not be prematurely operated; In aflatrate system,

without meters, this second reversal perhapscould be omitted, although it would stillbe necessary it reverse current supervision were

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